Deacylation of phosphatidylcholine (PC) and phosphatidylinositol (PI) occurs early in the sequence of metabolic events leading to activation of polymorphonuclear leukocytes (PMN). Rapid acylation of lysophospholipids also occurs and may be a source of new phospholipid for the cell during phagocytosis. Accompanying the phospholipid turnover is another series of reactions involving the action of the lipoxygenase system on arachidonic acid freed from PC and/or PI. The hydroxyeicosatetraenoic fatty acids (HETE), particularly 5-HETE, result from this pathway in the PMN. Rather than being released from the cell much of the HETE is reincorporated into phospholipid and its presence in the PMN membrane may play significant roles in activation. Acylation of phospholipids will be studied in both normal and Chediak-Higashi syndrome (CHS) PMN. The latter cells have abnormally formed granules, are chemotactically defective and display impaired HETE production. Lysophospholipids will be evaluated with respect to which are preferred substrates for acylation, particularly with 5-HETE. The effects of acylation inhibitors on stimulation of PMN will be assessed. The lipid mediator 1-0-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine will also be studied as a possible substrate for deacylation-recylation. The effects of exogenously added 5-HETE and platelet activation factor on chemotactic response of CHS PMN will be determined. Experiments will also be carried out employing electron spin resonance to determine what effects turnover of fatty acids and of lysophospholipids may have on membrane fluidity and surface charge. These studies should provide a better understanding of the role played by acylation in chemotactic stimulation of normal PMN and should expand our knowledge of the nature of the defect underlying abnormal chemotactic function of CHS cells. Experiments will also be carried out on PMN subjected to catalytic hydrogenation which will increase the degree of saturation of fatty acids. Functional abilities of such cells will increase our understanding of the role that unsaturated fatty acids play in PMN activation.